1. Field of the Invention
The present invention relates generally to a hand-propelled truck for carrying relatively large and heavy objects such as doors, and more particularly to a hand truck capable of adapting to the center of gravity of the object.
2. Description of the Prior Art
Hand trucks or dollies have been used for many years to move a variety of heavy objects. Normally, the hand truck is used by one person. It is typically designed having a lip or nose section for supporting the load, a frame for resting the load, a handle, a pair of wheels located at the bottom of the frame and occasionally a smaller pair of caster wheels for support and manuevering of the load. Braking systems are well known and they serve to lock the wheels in place when tilting the hand truck rearwards to the horizontal position.
The present invention provides a hand truck with an improved means for adjusting to a shift in the center of gravity of the load. This is essential for enabling a single person to handle a very heavy load.
Some prior art patents teach improved hand trucks having means for achieving some of the above objects. For instance U.S. Pat. No. 5,277,439 issued to George R. Pipes et al. on Jan. 11, 1994, depicts a hand truck that uses a pair of auxiliary wheels that swing away from the main frame, thereby allowing the load to be tilted backwards to a generally horizontal and stable position. The load rests on all four wheels and shows a much improved method over other prior patents. This invention requires the operator to control the movement of the main frame by a pull member whereas in the present invention no such mechanism is needed.
U.S. Pat. No. 4,919,442 issued to Thomas F. Green on Apr. 24, 1990, teaches the use of a leverage method for shifting the weights of the object to be carried. This patent basically forms a cart but not a hand truck that can be utilized as a work bench as well.
U.S. Pat. No. 5,445,399 issued to Frank S. Salvucci, Sr. on Aug. 29, 1995, shows a collapsable hand truck having a positive leg locking arrangement for a retractable leg. It utilizes a slide means for tilting the load. This invention does not seek to teach the ability of the hand truck to swing away from the main frame to form a horizontal work bench as does the present invention.
U.S. Pat. No. 3,968,974 issued to Nelson Wetzel on Jul. 13, 1976, teaches the use of a hand truck with an elaborate braking system. The present invention uses a very simple braking means.
U.S. Pat. No. 4,284,286 issued to Charles D. Lewallen on Aug. 18, 1987, describes a hand truck that utilizes auxiliary castor wheels to form a work table from a conventional hand truck. The present invention also forms a work bench, however it is the actual load (door) that provides the bench surface.
It is appreciated that the prior art addresses the need to more efficiently handle long or heavy objects with a simple hand truck. Some hand trucks have devices which secure the object to the truck and others have means for making adjustments for a changing center of gravity. It is evident that the hand truck of the present invention may be improved upon to a significant degree, and it is to this end, that this invention as shown and described herein is directed.
The invention is a self-propelled hand truck that utilizes the center of gravity of the load itself to assist a single operator in handling loads upwards of 400 pounds or more with a minimum of effort. The most pressing need that the invention addresses is in transporting doors that are often bulky and extremely heavy. It is recognized that the invention will perform equally as well transporting other loads, but for this specification the load will be assumed to be a door. The invention utilizes the weight of the load pivoting about a fulcrum point.
The invention includes a relatively rectangular main frame, upon which the door is placed. A pair of rectangularly shaped strut members support the main frame and the load thereupon. A pair of main wheels are attached to the forward strut for the purpose that wheels serve and a pair of auxiliary wheels (caster) are attached to the rear strut member for support and manueverability. A fulcrum assembly connects the frame to the struts. The frame and both struts can be extended in length to compensate for variations in lengths of the doors handled. The truck is relatively lightweight and manufactured from common materials, such as steel or aluminum. The strut and frame members are made from metal stock having a tubular and flat shape respectively.
Accordingly, it is a principal object of this invention to provide a hand truck that can be adjusted to the center of gravity of the load carried, thereby allowing the operator to utilize the weight of the load to assist him in handling it.
It is another object to provide a hand truck that will form a work bench whereby immediate repairs can be made.
It is a further object to provide a hand truck that is manufactured from the minimum number of parts and relatively inexpensive parts.
It is still another object of the invention to provide a hand truck that is capable of turning 360 degrees in its own tracks for manueverability.
And yet another object of the invention is to provide a hand truck for removing rather heavy and large doors, wherein the length and thickness of the door is not a factor.
It is another object of the invention to provide a hand truck that is collapsible for ease in moving and storage.
It is still another object of the invention to have the frame and support struts be capable of extension for handling extremely long doors.
And finally it is an object of the invention to provide a hand truck that will exhibit a high level of stability regardless of whether the load is vertical, tilted or horizontal to the ground surface.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.